Compressor units



Oct. 1, 1963 E. LWLER ETAL COMPRESSOR UNITS Filed June 2. 1960 UnitedStates Patent O 3,105,639 COMPRESSOR UNITS Erik Lwler, Stockholm,Sweden, and Iwan Ernst Roland kerman, Antwerp, Belgium, assignors toAtlas Copco Aktiebolag, Nacka, Sweden, a corporation of Sweden Filed.lune 2, 1960, Ser. No. 33,454 10 Claims. (Cl. 23d-31) This inventionrelates .to improvements in compressor units in which oil or othersuitable liquid is injected in the compression chambers of thecompressor for cooling, lubricating and sealing purposes. One object ofthe invention is to provide an improved control system for suchcompressor units. Other and more detailed objects will become apparentas the ensuing portion of this specification proceeds.

The invention is illustrated by way of example on the accompanyingdrawing, in which FIG. 1 illustrates diagrammatioally a two stagecompressor with oil injection and FIG. 2 illustrates a portion of thevalving arr-angements on a somewhat larger scale.

In the drawing 1 indicates the `air intake pipe to the compressor whichconsists of a low pressure portion 2 and a high pressure portion 3. Inthe illustrated embodiment the compressor portions 2 and 3 are screwtype compressors but the invention is also applicable to other types ofcompressors, such as sliding vane rotary corpressors, reciprocatingpiston compressors, or the like. The illustrated compressor is providedwith an air inlet casing 4 providing an inlet chamber 5 andcommunicating with the air intake pipe 1 through an air inlet controlvalve casing 6, in which a pneumatically balanced twin valve :orthrottle member 7, 8 is movable towards and away from seats 9, 10 inwhich lthe members 7 and S, respectively, t with a suitable clearance,permitting a very reduced flow of to the inlet chamber 5 in closedposition of the members 7, 8. The air compressed in the low pressureportion 2 of the compressor is conveyed through a chamber 11 to the highIpressure portion 3 and from said high pressure portion a dischargeconduit 12 conducts the compressed oil laden air over a spring loadedcheck valve 13 to a cyclone type oil separator 14 in which a rstseparation of the main portion of the oil in the compressed air takesplace. The separated oil is collected in an oil tank 15 on which theseparator 14 is provided. A conduit 16 conveys oil laden air from theseparator 14 to a second oil separator 17 which is disposed within anair receiver 18. The air receiver 18 is provided with an end cover 19 towhich the conduit 16 is attached and which together with the oilseparator 17 forms an admission chamber 20 in which some separation ofoil is `also produced. The oil laden air then passes through the filtersections or discs 21 of the separator 17 which take care of most of theremaining oil in the compressed air. The oil separator 17 is acylindrical body in which the filter discs 21 are provided and which isopen over the whole cross section towards the admission chamber 20 ofthe separator and provided with an end wall 21 at the outlet endcommunicating with an air receiver chamber 22 through an opening 23close to the top 'of `the separa-tor. A further opening 24 is providedin the end wall 21 at the bottom of the separator 17 for draining oilaccumulated in the lower portions of the separator to an oilaccumulation space 25 at the `bottom of the receiver chamber 22. Thereceiver 18 has a further chamber 26 encircling the separator 17 and thespace is partly separated from the receiver chamber 26 by a partition 27which extends upwards to about half the height of the separator 17. 28is an air discharge conduit which leads to the conventional air take-outof the compressor unit over a check valve 75. 29 is an automatic springloaded drain valve which opens at a certain low pressure, for instance 2kilogrammes per lsquare centimeter (kg/cm2) above atmospheric, in orderto drain otl any condensed water -accumulated in the receiver chamber26.

Two conduits 30 and 31 convey liquid oil accumulated at 32 in theadmission chamber 20 and at 25 in the receiver chamber 22 to separatesuction portions 33 and 34, respectively, of a gear pump 35 which pumpsthe oil back through a conduit 36 to the oil tank 15. The connections ofthe conduits 30, 31 to the pump 35 in the described manner makes itpossible to duly consider the difrerence in pressure between the spaces32 and 25. An oil pump 37 draws oil from the oil tank 15 through aconduit 38 and pumps oil through a conduit 39` to an oil cooler 40provided with a suitable cooling fan 41 mounted on or driven from thernain shaft -42 of the compressor. 43 is a spring loaded by-pass valvewhich is connectedV in parallel to the oil cooler 40 and 44 is a conduitfrom the oil cooler to an oil iilter 45 from which a conduit 46 leads toinjection nozzles 47, 48 in the compression chambers of the compressor.The by-pass valve 43l permits oil to iiow directly from the conduit 39to the conduit 44 when the resistance in the oil cooler is too great,for instance due to low oil temperature. A check valve 49 with 4a springloaded valve member 50l is provided in the conduit 46 which valve isloaded by a very weak spring `and by the difference in pressure betweenthe conduit 46 and the oil tank 15 which for this purpose is connectedto the bottom of the valve casing 49 through a conduit 51. 52 is anadjustable spring loaded by-pass check valve for the pump 37, thesetting of which controls the pressure on the oil injected in thecompression chambers of the compressor. Said valve also avoids excessiveoil pressures when oil temperature is low or compressor speed high.

The present compressor is unloaded through throttling of the .air intakepassage to the air intake chamber 5 by means of the balanced twinthrottle valve members 7, 8. The unloading device for the compressor iscombined with the twin valve members 7, 8. It consists of a piston Valvemember 53 provided in a housing 54 and connected to the kstem 55 yof thetwin valve members 7, 8. A conduit 56 forms a communication between thechamber 26 of the air receiver 1S and the housing 54, said conduit beingcontinued by a conduit 57 leading to the inlet chamber 58 in the airintake pipe 1. The passage in the conduit 57 is controlled by a needlevalve member 59 and the communication between the conduit 56 and theconduit 57 is controlled by the valve member 53 which has a transversepassage formed by la reduced portion or annular groove 6) on the member53 Iwhich in the extreme left hand position on the valve members 7, 8provides a communication between the conduit 56 'and the conduit 57 andthe intake chamber 58. A conduit 61 connects the air receiver 18 to acontrol valve 62 which is connected -to the end of the housing 54 by aconduit 63. The control valve has a vent passage 64 to which the conduit63 is connected when the control valve is inoperative.

When the compressor is at rest, a spring 65 moves the twin valve members7, 8 to the left in the figure so that the air intake to the compressoris throttled as tar as possible, the only passage to the air intakechamber 5 being the clearance between the members 7, 8 and the seats 9,10. Simultaneously the air receiver 18 is vented to the atmospherethrough the conduit 56, the groove 60, the conduit 57 and the air intakechamber 53. The control valve 62 is then in a position in which theconduit 63 is vented to the atmosphere through the vent passage 64 andthe passage in the control valve to the conduit 61 is closed.

The stem 55 of the twin valve members 7, 8` is also connected to apiston 66 which is movable in a valve casing 67 which also contains apiston valve 68 loaded by a spring 69 and connected by a rod 70 to abutton 71. A conduit 72 connects the pressure oil conduit 39 with thecasing 67. The opening 73 of said conduit in the casing 67 is controlledby the valve member 68.

When the compressor is at rest no oil pressure exists in the conduit 39and consequently there is no oil pressure in ,the conduit 72 and in thespace 74 in the housing 67. The spring 69 therefor moves the valvemember 68 to close position.

When the compressor is started the twin valve members 7, 8 throttle 'theair liow to the inlet chamber 5 so that a certain vacuum is produced insaid chamber. The compressor now runs idle and only a small quantity ofcompressed air is delivered to the receiver 18, which air ows back tothe intake chamber 58 through the conduit 56, groove 60, conduit 57, andvalve 5h which latter controls the pressure in the receiver 18 when thecompressor runs idle and unloaded. Oil is injected in the compressionchambers when the compressor runs idle but the valve member 68 preventspressure oil from reaching the space 74. By running the compressor idleas described it is possible to run the engine and compressor Warm.

Now, if it be desired to load the compressor, the button 71 is pulled sothat the valve 68 opens the passage from conduit 72 to the space 74causing oil pressure from the compressor oil pump 37 to act on thepiston 66 and to move it to the right in the figure so that the twinvalve members 7, 8 are moved to open position. The air flow throughconduit 56 is simultaneously interrupted by the vpiston valve member 53,and the compressor continues to operate in this condition until acertain pressure, for instance 7 kilogrammes per square centimeter aboveatmospheric, has been reached. Then the control valve 62 opens a passagefrom the conduit 6i to the conduit 63 causing the piston valve S3 andthe twin valve members 7, 8 [to move to the left in the ligurev so thatthe air intake is throttled. Thevcommunication between the conduit S6and the intake chamber 53 is opened and a small quantity of air flowsfrom the receiver 1S to the intake chamber 58. The compressor now runsunloaded with full pressure on the air receiver 18. The air quantitytiowing to the receiver when the compressor runs idle or unloaded kasabove described is sufficient to carry the simultaneously injectedcooling oil to the oil separators.

When the pressure in the air receiver has been reduced to a certainextent, for instance to 61/2 kilogrammes per square centimeter aboveatmospheric the control valve 62 interrupts the communication betweenthe conduits 61 and 63 and connects the conduit 63 to the vent passage64 so that the conduit 63 is vented to the atmosphere which permits theoil pressure in the space 74 to move the twin valve members 7, 8 to theright in :the gure thereby reloading the compressor which immediatelystarts to deliver compressed air `to the receiver 18. Sirnultaneously,the piston valve 53 closes the communication between the conduit 56 .andthe conduit 57 and the air pressure in the receiver continues to riseuntil it again reaches the maximum limit, for instance 7 kilogrammes persquare centimeter above atmospheric.

It will be appreciated that with the above arrangement failure of theoil pump 37 to deliver pressure oil causes valve members 7, Sto move toclosed position and the valve member 68 to close the opening 73, so thatthe compressor cannot produce `compressed air for useful work until thedefect in the oil injection system has been corrected. Y

It should also be observed that when the compressor has stoppedcompressed air in the 'air receiver 18 cannot ilood the compressor withoil since in the absence of oil pressure in the conduit 46 air pressurein the oil tank 1S keeps the valve member 50 closed. The dischargeconduit 28 of the compressor contains an automatic spring 4 loaded checkvalve 75 which lwhen the compressor delivery is interrupted preventsback flow of compressed air from the network connected to the dischargeconduit 28. The invention may be modified in various diiterent wayswithin the scope of the claims and the above embodiment is onlyydescribed as van example.

What We claim is: A Y 1. In a `compressor unit, a compressor having acompression chamber, means for injecting cooling liquid in saidcompression chamber, means for conveying compressed uid vfrom saidcompressor, a iluid intake conduit leading to the compressor Aforintroducing iluid to be compressed therein, throttle valve meansoperablein said intake conduit from a rst position in which uid flow tothe compressor is partially restricted to a second position in whichfluid is unrestrictedly admitted to the compressor and vice versa, meansfor selectively opening said throttle valve means from said firstposition towards said second position, means for closing said throttlevalve means from said second position towards saidrhst position, saidopening means being operatively responsive to pressure in said .coolingliquid injecting means, and saidV closing means being operativelyresponsive to pressure in said compressed iluid conveying means.

.2. In a compressor unit, a `compressor having a compression chamber,means for injecting cooling liquid into said compression chamber,acompressed tluid receiver, means for conveying compressed tluid Ifromsaid compresser to said receiver, means for separating cooling liquidfrom said compressed Huid, a iluid intake conduit leading to thecompressor for introducing iiuid to be compressed therein, throttlevalve means operable in said intake conduit from a first throttlingposition` in which fluid flow to the compressor is restricted to asecond open position in which iluid is admitted fto Ithe compressorandvice versa, means operatively connected with said cooling Y saidcompression chamber, a iluid intake conduit leading to the compressorfor introducing uid compression therein, throttle valve means operablein Said intake conduit from Ya iirst position in which fluid ilow to thecompressor is restricted to a second position in which iiuid is admittedto the compressor and vice versa, piston means for moving the throttlevalve means from said first position towards said second position, andmeans operatively connecting said piston means with said means forinjecting cooling liquid effecting said movement of said throttle valvemeans lby said piston means in response 'to a predetermined pressure insaid cooling liquid injecting means.

4. A compressor unit according to claim 3, in which* a manually operablevalve is provided for controlling the action of said pressure in saidcooling liquid injecting .j

means to move said piston means and said throttle valve means from saidfirst position towards the second position.

5. In a compressor unit, a compressor having a compression chamber, pumpand conduit means for injecting cooling liquid into said compressionchamber, a coms pressed fluid receiver, conduits means 4for conveyingcornvided on a common valve stern and operable in said intake conduitfrom a rst throttling position in which Huid ow to the compressor isrestricted to :a second open position in which fluid is admitted to:said compressor and vice versa, a spring urging said throttle valvemember towards said iirst position, a iirst cylinder-and-piston valvemeans for removing said throttle valve mem-ber toward said irstthrottling position thereof, a regulating valve member communicatingwith both said receiver and iirst cylinder-and-piston means and operableto admit compressed pressure -uid from said receiver to said iirstcylinder-and-piston upon attainment of a certain pressure in saidreceiver for moving said cylinder-and-piston valve means and saidthrottle valve members towards said iirst position, means for ventingpressure iiuid from the first cylinder-and-piston valve means permittingmovement thereof away from said first position toward said secondposition, a second cylinder having a piston movable therein and attachedto said throttle valve stem, and means for introducing cooling liquidpressure into said second cylinder eective on said piston for movingsaid -piston and the throttle valve members from said first positiontowards said second position upon said venting of said firstcylinder-and-piston valve means.

6. In a compressor unit, a fluid compressor having a compressionchamber, means for conveying compressed iiuid from said compressor, afluid intake conduit leading to the compressor, throttle valve meansoperable in said intake conduit from a n'irst position tin which fluidiiow to the compressor is restricted to a second position in which fluidis admitted to the compressor and vice versa, an oil pump operated whensaid compressor is operated to provide pressure oil, means for movingsaid throttle valve means from said rst position towards said secondposition in response to oil pressure produced by said oil pump, andmeans for moving the throttle valve means from said second positiontowards said iirst position in response to attainment of a certain fluidpressure in said uid conveying means.

7. -A compressor unit according to claim 6 having a rst conduit Iforconveying pressure oil from the oil pump to said compression chamber ofthe compressor for cooling and lubricating the compressor and a secondconduit for conveying pressure oil from the oil pump to said throttlevalve means for operation of the throttle valve means.

8. lIn an air compressor unit of the character described for supplyingand maintaining compressed air in a receiver therefor from which saidcompressed air is withdrawn for use under pressure, the combinationwhich comprises an air compressor having a compression chamber therein,air intake means 4for introducing air into sa-id compression chamber forcompression therein, a compressed air conduit for conducting compressedair from said compressor to said receiver, throttle valve means in saidair intake and movable therein from a first throttling position in whichflow of air through said intake into said compression chamber issubstantially restricted into a second open position in which said yiiowof air through sad air intake is substantially unres-tricted by saidthrottle valve means, pump and conduit means for injecting cooling oilunder pressure into said compressor, a liquid-operated piston means formoving said throttle Valve means from said first throttling positiontoward said second open position thereof, means for selectivelyintroducing liquid pressure into said piston means from said coolingliquid pump and conduit ymeans for said movement of said throttle valvemeans, an air-operated piston means for moving said throttle valve meansfrom said second open position thereof toward said first throttlingposition, means :for introducing compressed air pressure from saidreceiver into said air-operated piston means, and control meansoperatively responsive to the pressure of said compressed air in saidreceiver and to the pressure in said cooling liquid pump and conduitmeans for selectively and alternatively introducing said air pressure tosaid air-operated piston and said liquid pressure to saidliquid-operated piston for determining said movements of said throttlevalve means toward and away from said two positions thereof in responseto the maintenance of a predetermined air pressure in said compressedair receiver.

9. Apparatus as recited in claim 8 which also includes spring means forurging said throttle valve means into said throttling position thereofindependently of the air pressure in said receiver and upon a decreaseof pressure in said cooling liquid pump and conduit means below apredetermined minimum value.

V10. Apparatus as reciited in claim 8 which also includes check valvemeans between said compression chamber and said cooling liquid pump andconduit means for interrupting iiow of said cooling liquid to saidcompression chamber when said compressor is not running.

References Cited in the file of this patent UNITED STATES PATENTS2,234,471 FteS Mar. 11, 1941 241,192 Freeman May 6, 1941 2,241,7'1'8MeXSell May 13, 1941 2,272,9@6 Squillel' Feb. 10, 1942

8. IN AN AIR COMPRESSOR UNIT OF THE CHARACTER DESCRIBED FOR SUPPLYINGAND MAINTAINING COMPRESSED AIR IN A RECEIVER THEREFOR FROM WHICH SAIDCOMPRESSED AIR IS WITHDRAWN FOR USE UNDER PRESSURE, THE COMBINATIONWHICH COMPRISES AN AIR COMPRESSOR HAVING A COMPRESSION CHAMBER THEREIN,AIR INTAKE MEANS FOR INTRODUCING AIR INTO SAID COMPRESSION CHAMBER FORCOMPRESSION THEREIN, A COMPRESSED AIR CONDUIT FOR CONDUCTING COMPRESSEDAIR FROM SAID COMPRESSOR TO SAID RECEIVER, THROTTLE VALVE MEANS IN SAIDAIR INTAKE AND MOVABLE THEREIN FROM A FIRST THROTTLING POSITION IN WHICHFLOW OF AIR THROUGH SAID INTAKE INTO SAID COMPRESSION CHAMBER ISSUBSTANTIALLY RESTRICTED INTO A SECOND OPEN POSITION IN WHICH SAID FLOWOF AIR THROUGH SAD AIR INTAKE IS SUBSTANTIALLY UNRESTRICTED BY SAIDTHROTTLE VALVE MEANS, PUMP AND CONDUIT MEANS FOR INJECTING COOLING OILUNDER PRESSURE INTO SAID COMPRESSOR, A LIQUID-OPERATED PISTON MEANS FORMOVING SAID THROTTLE VALVE MEANS FROM SAID FIRST THROTTLING POSITIONTOWARD SAID SECOND OPEN POSITION THEREOF, MEANS FOR SELECTIVELYINTRODUCING LIQUID PRESSURE INTO SAID PISTON MEANS FROM SAID COOLINGLIQUID PUMP AND CONDUIT MEANS FOR SAID MOVEMENT OF SAID THROTTLE VALVEMEANS, AN AIR-OPERATED PISTON MEANS FOR MOVING SAID THROTTLE VALVE MEANSFROM SAID SECOND OPEN POSITION THEREOF TOWARD SAID FIRST THROTTLINGPOSITION, MEANS FOR INTRODUCING COMPRESSED AIR PRESSURE FROM SAIDRECEIVER INTO SAID AIR-OPERATED PISTON MEANS, AND CONTROL MEANSOPERATIVELY RESPONSIVE TO THE PRESSURE OF SAID COMPRESSED AIR IN SAIDRECEIVER AND TO THE PRESSURE IN SAID COOLING LIQUID PUMP AND CONDUITMEANS FOR SELECTIVELY AND ALTERNATIVELY INTRODUCING SAID AIR PRESSURE TOSAID AIR-OPERATED PISTON AND SAID LIQUID PRESSURE TO SAIDLIQUID-OPERATED PISTON FOR DETERMINING SAID MOVEMENTS OF SAID THROTTLEVALVE MEANS TOWARD AND AWAY FROM SAID TWO POSITIONS THEREOF IN RESPONSETO THE MAINTENANCE OF A PREDETERMINED AIR PRESSURE IN SAID COMPRESSEDAIR RECEIVER.